Masking Camera rendering,Simulate reduced field of view with camera mask

Effect

To be honest the shader code I've written might be wrong... but it works for me and it's short so :shrug:

Setup

Make two cameras that see the same things:

• Make two cameras, one called RealWorldCam, the other called 'ARCam'.

• Delete one of their audio sources (you can only have one in view, not really related but you'll get warnings when running)

• Make an empty game object called 'Cameras'

• Make both cameras children of 'Cameras' and make sure they are at the correct position

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Setup layers for each to view

• In the top right of the screen there is a drop down called 'Layers', click it and go to 'Edit Layers...'

• Add two new layers, one called 'Mask' and one called 'AR'

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• Go to your 'ARCam' and click the dropdown for 'Culling Mask'

• Edit it to include Everything EXCEPT 'Mask' layer.

• Make sure the depth is '-1'

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• Go to your 'RealWorldCam' and click the dropdown for 'Culling Mask'

• Edit it to include Everything EXCEPT 'AR' layer.

• Change the depth to '0'

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Make the mask

• Add an object to the scene that is the shape you want your mask and call it 'mask'

• Position it in front of the cameras so that it covers the area you want to become AR (it doesn't matter how near or far from the camera it is)

• Make it a child of the 'Cameras' object (just so it stays at the correct relative position)

• In the inspector, change its layer to 'Mask'

• Create a new shader in unity and copy in the code from below

• Create a new material called 'mask' and make it use the shader

• Make your 'mask' object use the new 'mask' material

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Make real world objects

• By default when you make a primitive it will be viewable in all areas of the screen, this is because it will not belong to the layer 'AR'

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Make some AR only objects

• Add an object to your scene

• In the inspector change the layer to 'AR'

• It should now only be viewable when it overlaps with your 'mask' object in the camera

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Make some AR only UI

• If you want to have UI outside of your AR you will need to canvases

• Call your AR canvas 'ARCanvas'

• Click on the ARCanvas and in the inspector look under the header 'Canvas'

• Change the Render Mode to 'Screen Space - Camera'

• Change the camera to 'ARCam'

• If you want it to act like an overlay render camera then set the plane distance to '0.31' (this number is chosen as it is the default near clipping plane value of the ARCam + 0.01)

• Alternatively you can also use a world space UI, in this case you need to set the layer of the canvas and it's children to 'AR'

• Not sure if it is possible to get overlay space to work, I somewhat doubt it, since overlay implies it will render afterwards regardless of setup.

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Mask shader code

 Shader "Custom/ARMask" {
     SubShader{
         Tags { "RenderType" = "Opaque" "Queue" = "Geometry-1" }
         Pass {
             Blend Zero One
             ZWrite On
         }
     }
 }